Effect of Diaphragm Plication in Thymoma Patients with and without Myasthenia Gravis.

Background: Thymoma is the most common tumor of the anterior mediastinum that has the most effective treatment, as it can be completely resected. In patients with advanced stage, phrenic nerve involvement can be seen and suggested treatment for these patients is unilateral phrenic excision and diaphragm plication. However in patients with myasthenia gravis, there are concerns in relation to this method of treatment. The aim of this study is to evaluate the effects of plication of the diaphragm on complications of phrenic nerve excision in thymoma patients with and without myasthenia gravis involving the phrenic nerve. Materials and Methods: A retrospective cohort study was performed on 26 patients with thymoma; half of the patients had myasthenia gravis and the other half did not have myasthenia gravis. We performed diaphragm plication in 7 patients in each group with excision of phrenic nerve. Patients were evaluated based on preoperative and postoperative variables. Results: The patients' age (P=0.943), sex (P=0.999), blood loss during surgery (P=0.919), need for transfusion during surgery (P=0.999), short term complications (P=0.186), need for tracheostomy (P=0.27) and mortality (P=0.09) differences were not significant. However, the average duration of ICU stay (P=0.001) and intubation in ICU (P=0.001) in patients who had myasthenia gravis was more than patients without myasthenia gravis. These values were less in patients with myasthenia gravis and diaphragm plication than patients with myasthenia gravis and no diaphragm plication. Conclusion: Excision of the phrenic nerve in patients with myasthenia gravis associated with thymoma and phrenic nerve involvement is appropriate.


INTRODUCTION
Thymoma is a thymic epithelial cell neoplasm that easily relapses and gives metastasis. Thymoma is the most common tumor of the anterior mediastinum (1,2). The most effective treatment of thymoma is complete removal of the thymus surgically (2,3). In 33% of those with advanced stages [III, IV] of thymoma, phrenic nerve involvement can be seen (3). Suggested treatment for patients with phrenic nerve involvement is unilateral excision of involved phrenic nerve. This procedure does not cause a significant problem in adults, and hemidiaphragm paralysis causes 20 to 30 percent decrease in vital capacity and total lung capacity (2). In these patients, diaphragm plication is performed in addition to phrenic nerve excision. Plication of the diaphragm increases lung expansion and prevents paradoxical movement of the diaphragm (4)(5)(6). This procedure is very useful for patients who suffer from phrenic nerve injury and resultant shortness of breath (4,5).
There are concerns about the possibility of phrenic nerve injury in patients with bilateral phrenic nerve involvement, minimal involvement of phrenic nerve, people with respiratory problems before surgery, thymoma accompanied by myasthenia gravis and young people who need multiple chest surgery (3). Therefore, in these patients radiotherapy is used after thymectomy to preserve the phrenic nerve (3,7). Survival is the same in patients with excision of phrenic nerve in comparison with the patients without excision of phrenic nerve. Of course, in this method, there is the possibility of recurrence of thymoma (2,3). There are measures to choose the appropriate method of treatment in patients with thymoma and phrenic nerve involvement. One of them is the presence or absence of myasthenia gravis in association with thymoma (2).
The aim of this study is to evaluate the effects of plication of the diaphragm on complication of phrenic nerve excision in thymoma patients with and without myasthenia gravis involving the phrenic nerve.         Table 3). The mean duration of intubation [day] was the most in the group B2 and the least in group A1, but there was no significant difference between group A1 and A2 (P=0.816). Also there was no significant difference between group A1 and A2 in terms of ICU stay (P=813). Duration of ICU stay was the most in group B2 and the least for group A1. Although complication with significancy shows better result in non myasthenia group than with myasthenia group, better result shows in group with plication versus without plication in 2 groups without significancy.

DISCUSSION
The phrenic nerve is formed from C3,C4,C5 roots (8,9,10). The phrenic nerve lies in front of anterior scalene muscle and before entering the thorax, it passes in front of the subclavian artery (11). It comes down in front of the pulmonary hilum between pericardium and parietal pleura. This nerve consists of sensory-motor and sympathetic fibers. This is the only motor nerve of the diaphragm and provides sensory fibers of the pericardium, mediastinal pleura and peritoneum of the diaphragm. This is the reason of importance of this nerve in respiratory cycles (9,10). So, this nerve should be preserved in thoracic surgery (12). Injury to this nerve results in hemidiaphragm paralysis and paradoxical movement of the diaphragm and causes respiratory problems (8,9,11,13).
Diaphragm paralysis following injury to this nerve is more harmful in pediatric population than in adults, because respiration is not exclusively dependent to diaphragm function in adults (13 (16). The results of Welvaart's study showed increase in tidal volume and decrease in respiratory frequency after plication, but no change in maximal exercise capacity (6).
Jedrzejowicz and colleagues found that maximal static expiratory and inspiratory mouth pressure reduced in 16 of 17 patients with myasthenia gravis and also vital capacity was abnormal in 12 of the patients and transdiaphragmatic pressure reduced in 8 patients. There was no relationship between the grade of myasthenia gravis with the severity of dyspnea and muscle strength (17).

CONCLUSION
Excision of the phrenic nerve in patients with myasthenia gravis associated with thymoma and phrenic nerve involvement is appropriate.